Filter sheet



May 27, 1952 D. c. KNOWLTON FILTER SHEET Filed Aug. 5, 1949 WEEKINVENTOR. DAVID C. KNOWLTON BY 6 44mm G MJMQ HIS A'fTORNEY Patented May27, 1952 UITED STATES ,1;-

TENT OFFICE FILTER SHEET Application August 3, 1949, Serial No. 108,326

6 Claims. 1

This invention relates to a filter sheet provided with deformed portionsto make it stretchable longitudinally and transversely, and a filterpress having filter sheets of this construction interposed between therecessed plates.

In chamber filter presses with filter sheets disposed between therecessed plates, cloth filter sheets have heretofore been generally usedas they have the ability to stretch to a limited extent when forced intothe recesses of the recessed plates. However, too great a strain isoften exerted upon the cloth where the amount of solids to be separatedfrom the liquid is large, and hence fiush plates are then frequentlyused with distance or spacing frames inserted between the fiush plates.Paper filter sheets have been used to a limited extent and usually inconjunction with the cloth in those instances where paper sheets havebeen used. Paper sheets have not been adapted to be used alone becauseof their inability to stretch longitudinally and transversely, and,therefore, are not strong enough to stand the strain to which they aresubjected. Accordingly, when paper sheets are used in conjunction withcloth sheets, they needed to be placed between the cloth sheets so as tobe supported by the cloth sheets and be held in place thereby should thepaper sheets break, especially where a loose granular filtering materialis confined between the filter sheets. Even should the paper sheets notbe torn or ruptured in being stretched, they are, thereby, weakened andimpaired as are the cloth filter sheets when subjected to too great astrain. This results even with cloth sheets when, as above pointed out,they are subjected to too great a strain, and thus their use withrecessed filter plates is limited to the filtering of liquid containingsmall quantities of solids.

Cloth is expensive and much time and effort are expended in cleaning,and repairing it, when necessary, for reuse. Therefore, it would behighly desirable to use paper filter sheets so that they could bedisposed of and replaced with new ones after they have become cloggedwith accumulated precipitated solids. Accordingly, the paper, inaccordance with my invention, is provided with longitudinal andtransverse deformed portions, such as crepes or corrugations, forpermitting it to be stretched transversely and longitudinally. Theextent of the stretch can thus be controlled, and the filter sheets canbe constructed to have the necessary stretch to which they will besubjected by reasorf of the recesses in the plates in the filteringoperation.

One of the principal objects of my invention is to provide a feltedfilter sheet which is stretchable longitudinally and transversely.

Another object of the invention is to provide a filter paper suitablefor use in a recessed plate filter pressso that it can be disposed ofrather than cleaned for reuse.

Another object of the invention is to provide a filter paper which maybe used alone with the recessed plates in a filter press.

Another object of the invention is to provide paper sheets for beinginterposed between the recessed plates of a filter press and besufiiciently stretchable to conform to the recesses in said recessedplates.

Further objects and objects relating to the details of construction andeconomies of operation will definitely appear from the detaileddescription to follow. In one instance I have accomplished the objectsof my invention by the device and means set forth in the followingspecification. My invention is clearly defined and pointed out in theappended claims. Filter sheet structure constituting preferredembodiments of my invention and for carrying out the invention isillustrated in the accompanying drawings forming apart of thisspecification, in which:

Fig. 1, is a longitudinal cross sectional view of a portion of a filterchamber press, with the recessed plates, equipped with filter sheetsembodying my invention.

Fig. 2 is a perspective view of an embodiment of a paper filter sheetembodying my invention.

Fig. 3 is a perspective view of another embodiment of a paper filtersheet embodying my inven-' tion.

Referring specifically to the drawings in which like numerals are usedto designate like parts, numeral 2 refers to one of two opposite endplates between which any number of recessed plates 3 are secured withfilter sheets 4 interposed between the plates. The end plate is recessedat 5 on the side next to the adjacent recessed plate 3, and each of theplates 3 is recessed on opposite sides with a recess 6, like recess 5,in the inner side of the end plates. The recesses in the end andintermediate plates are bounded by surrounding fianges I which abut whenthe plates are clamped together to enclose the recesses.

The filter press is of the general type of construction shown anddescribed on pages 345 to 348 of Principles of Chemical Engineering byWalker, Lewis and McAdams (second edition) which was published byMcGraw-Hill Book Company, Inc. Reference is made to this publication forincorporation herein as a part of the disclosure for showing chamberfilter press constructions with the recessed plates between which filtersheets 4 of the present invention are placed.

. Two filter sheets are placed between the adjacent recessed plates. Onesheet 4a, covers the single recess 5 in the end plate, and then therecesses B on opposite sides of the intermediate plates are covered bysheet 4b which is long enough to have an intermediate part draped overthe top of an intermediate plate'with the free endsof the sheetextending downwardly over the opposite faces of the recessed plates tobe clamped between the adjacent recessed plates.

Each plate is provided with a hole in one corner to register and be inalignment for forming a longitudinal channel 8 through which material tobe filtered is flowed between the adjacent re cessed plates and filtersheets to pass through the filter sheets, and a mass of granularmaterial 9 which may, if desired, be contained between the filtersheets, to flow down the bottom walls of the recesses, usually providedwith channels, to be discharged out through petcocks in in the bottom ofeach of the plates.

In the filtering operation, the filter sheets are stretched into therecesses 5' and 6 within the recessed plates, and heretofore only acloth or textile sheet could be used since it could stand a limitedstrain. Paper andsuchfeltedmaterial has not been suitable because itcould not stand even the limited strain required. Under the conditionsin the filtering operation, as noted above, a too great a strain isexerted even upon cloth sheets, and it has been the practice to useflush plates with distance frames interposed, rather than recessedplates, when a large amount of solids needed to be filteredfrom theliquid.

In order to give the filter sheets the ability to stretch in bothlateral directionsand prevent tensile strain upon them, they areprovided with deformed portions to increase their area. These deformedportions may be crepes ll (Fig. 2) or corrugations i2 (Fig. 3), theerepes or corrugations being arranged-so that there is an increased areasurface bothlongitudina-lly and transversely, thereby makingprovisionfor the paper to be stretched in either or both later-a1directions without subjecting it to undue strain. There is no tensilestrain upon the paper until after the deformed portions havebeenstretched to a substantially fiat condition, and thus the deformedportions can be made to give a predetermined stretch and have the paperfiat when it has-been subjected to maximum stretch for conforming to thewalls of the recesses. The invention is not limited to any particularshape or arrangement of the crepes or corrugations, and they may be ofany size and arrangement and-in regular or irregular pattern or design.Howevenin whatever form or size they are made, they will-besufficient toprovide for the necessary stretch'for the paper to conform to therecesses in the recessed plates before being flattened-out. Accordingly,filtersheets so constructed can be stretchedwith out being subjectedto'tensile strain thatwould impair their strength and structure. Thedeformed portions are pressed from the general plane of the sheetto liein a'plane outside of said general plane. Y

The operation of the filter press with the recessed plates is fullydescribed in the above referred to publication, and'the operationof afilter equipped with the filtersheets as described in the instant caseis'ex'actlythe same as when cloth filter sheets are used. The clothsheets, heretofore, used permitted limited stretch in oppositedirections because of the stretchability of the fibers comprising thecloth or the woven structure of the cloth. The cl'oth has not, however,

been provided with deformed portions, such as crinkles, embossments,corrugations and the like which are provided in the filter sheets of thepresent invention, thereby making paper suitable for use as filtersheets with the recessed filter plates.

The ore es and corrugations may be formed in various ways, and theinvention is not limited to any particular way of forming them so longas they are angularly disposed to each other to give stretchhorizontally in opposite linear directions. They may be angularlydisposed to each other and arranged diagonally rather than lengthwiseand crosswise of the sheet. For example, the corrugations may bedisposed at right angles to each other as in Fig. 3 but arranged at a 45angle to the direction of the sheet in being corrugated. Then, too, thesheet may be creped in one direction and corrugated in the otherdirection rather than be corrugated in both directions as illustrated inFig. 2. These are suggestions of some variations which may be made incarrying out my invention.

I am aware that the structure herein shown is susceptible ofconsiderable variation and that there may be wide variation in makingthe deformed portions of the filter sheet without departing from thespirit of my invention and, therefore, I have claimed my inventionbroadly as indicated in the appended claims.

Having thus described my invention, what I claim as new and useful, anddesire to secure by United States Letters Patent, is:

1. In combination with recessed plates of a filter press in which therecesses of the plates are formed by the bottom wall surface in a planebelow the face of the surrounding abutting wall on said plates, a feltedfilter sheet interposed between adjacent plates and bridging therecesses, said filter sheet having portions pressed from its generalplane to lie in a plane outside of the general plane for rendering saidsheet transversely and longitudinally stretchable.

2. The combination of claim 1 in which the pressed portions areangularly disposed to each other.

3. The combination of claim 1 in which there is at least one filtersheet adjacent each of the recessed plates.

i. The combination of claim 1 in which the pressed portions aretransversely and longitudinally disposed.

5. The combination of claim 2 in which pressed portions are transverselyand longitudinally disposed.

6. The combination of claim 2 in which there is at least one filtersheet adjacent each of the recessed plates.

DAVID C. KNOWLTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 235,698 Newton Dec. 31, 18801,175,001 Mangelsdorff Mar. 14, 1916 1,785,494 Revel Dec. 16, 19301,796,794 Koppelman Mar. 17, 1931 2,019,903 Heitmann Novy5, 19352,245,014 Sherman June 10, 19 2,298,980 Sloan et a1 0017.13, 19422,375,246 Kasten May' 8,1945

